Coating compositions in which all of the components are stored together in a single container, often known as 1-K compositions, are desirable in many cases from the standpoint of, for example, convenience to the end user. Among the properties that such coating compositions should exhibit is storage stability. In other words, the viscosity of the composition should not significantly increase over time to the point in which the composition is no longer suitable for convenient use for depositing a coating.
In many cases, it is desirable to use liquid coating compositions that are borne in water as opposed to organic solvents. This desire stems primarily from environmental concerns with the emission of volatile organic compounds (“VOC”) during the painting process.
It is also often desirable to provide coating compositions that are curable under ambient conditions of atmospheric temperature and pressure. Such compositions are, in many cases, preferable over, for example, thermally-cured or radiation cured coating compositions because (i) little or no energy is required to cure the composition, (ii) the materials from which some substrates are constructed cannot withstand elevated temperature cure conditions, and/or (iii) large or complex articles to be coated may not be convenient for processing through thermal or radiation cure equipment.
One solution for achieving a 1-K, waterborne, ambient curable coating composition is to employ a carbonyl group-containing polymer emulsion containing a polyhydrazide compound crosslinker. As water in the emulsion evaporates after the emulsion is applied to a substrate, the hydrazide groups and the carbonyl groups crosslink as a result of dehydration condensation to form a cured film. While various improvements in 1-K, waterborne coating compositions utilizing carbonyl-hydrazide chemistry have been made over the years, it is still desireable to provide further improved compositions.
For example, in certain applications, the coatings may need to be suitable for application to various kinds of substrates, including various plastics and metals, and must exhibit excellent adhesion to each of them. In addition, in certain applications, such as when the coating composition is applied to medical equipment (among other things), the coating must be especially resistant to both water and alcohol. As a result, it would be desirable to provide 1-K, waterborne, ambient curable coating compositions based on carbonyl-hydrazide chemistry that exhibit excellent adhesion to plastic and metal substrates and which exhibit excellent water and alcohol resistance.